Secondary battery including one-way exhaust member

Abstract

Disclosed herein is a plate-shaped secondary battery constructed in a structure in which an electrode assembly of a cathode/separator/anode structure is mounted in a battery case, and the battery case is sealed by thermal welding, wherein the secondary battery has at least one-way exhaust member, mounted at a sealed portion, formed at the outer circumference of an electrode assembly receiving part of the battery case, for allowing internal high-pressure gas to be exhausted out of a battery cell and preventing external gas from being introduced into the battery cell. The secondary battery according to the present invention has the effect of effectively exhausting internal high-pressure gas generated during the abnormal operation of the battery, such as overcharge, out of the battery case, while maintaining the sealability of the battery case, thereby simultaneously improving the efficiency and safety of the battery.

What is claimed is: 
     
       1. A plate-shaped secondary battery constructed in a structure in which an electrode assembly of a cathode/separator/anode structure is mounted in a battery case, and the battery case is sealed by thermal welding, wherein
 the secondary battery has at least one-way exhaust member, mounted at a sealed portion, formed at the outer circumference of an electrode assembly receiving part of the battery case, for allowing internal high-pressure gas to be exhausted out of a battery cell and preventing external gas from being introduced into the battery cell, 
 wherein the one-way exhaust member includes: 
 a first film attached to the sealed portion, 
 a porous film constructed in a structure in which the outer circumference, of the porous film, excluding an upper end opening of the one-way exhaust member, is coupled to the first film, and the upper end of the porous film is lower than that of the first film, 
 a variable film constructed in a structure in which the outer circumference of the variable film, excluding the upper end opening of the one-way exhaust member, is coupled to the porous film, the lower end of the variable film is coupled to the porous film at a position where the lower end of the variable film is spaced apart from the lower end of the porous film by a predetermined width, and the upper end of the variable film is higher than that of the porous film, the variable film being made of a material more flexible than that of the porous film or having a thickness less than that of the porous film, and 
 a second film constructed in a structure in which the second film is attached to the sealed portion at the opposite side of the first film, and the outer circumference of the second film, excluding the upper end opening of the one-way exhaust member, is coupled to the lower end of the variable film, 
 wherein the variable film is movable between a position contacting the first film and a position separated from the first film, such that, when the variable film is in the position contacting the first film, the variable film prevents external gas from being introduced into the battery cell through the one-way exhaust member, and when the variable film is in the position separated from the first film, internal high-pressure gas can be exhausted out of a battery cell through the one-way exhaust member. 
 
     
     
       2. The secondary battery according to  claim 1 , wherein the battery case is made of a laminate sheet including a resin layer and a metal layer. 
     
     
       3. The secondary battery according to  claim 2 , wherein the sheet is an aluminum laminate sheet. 
     
     
       4. The secondary battery according to  claim 1 , wherein the electrode assembly is constructed in a folding, stacking, or stacking/folding type structure. 
     
     
       5. The secondary battery according to  claim 1 , wherein the variable film is made of an elastic material, and the upper end of the variable film is bent toward the first film. 
     
     
       6. The secondary battery according to  claim 1 , wherein the upper end of the first film is in contact with the upper end of the second film during the normal operation of the battery. 
     
     
       7. The secondary battery according to  claim 1 , wherein the upper end opening of the one-way exhaust member is formed in the sealed portion such that the upper end opening of the one-way exhaust member communicates with the outside of the battery cell. 
     
     
       8. The secondary battery according to  claim 1 , wherein the upper end opening of the one-way exhaust member is closed by the sealed portion by a predetermined width. 
     
     
       9. The secondary battery according to  claim 8 , wherein the width of the sealed portion closing the upper end opening of the one-way exhaust member is 10 to 60% that of the total width of the sealed portion. 
     
     
       10. The secondary battery according to  claim 1 , wherein the porous film is as gas and liquid separation film. 
     
     
       11. The secondary battery according to  claim 1 , wherein the battery is a lithium secondary battery. 
     
     
       12. The secondary battery according to  claim 1 , wherein the electrode assembly is connected, to electrode terminals extruding out of the battery case. 
     
     
       13. The secondary battery according to  claim 12 , wherein the electrode terminals are formed at a shot side of the battery case together, or the electrode terminals are formed at a short side of the battery case as opposed structure each other. 
     
     
       14. The secondary battery according to  claim 12 , wherein the electrode terminals are formed at a long side of the battery case together, or the electrode terminals are formed at a long side of the battery case as opposed structure each other. 
     
     
       15. A middle- or large-sized battery pack of high output and large capacity, including a secondary battery according to  claim 1  as a unit cell. 
     
     
       16. A plate-shaped, secondary battery constructed in a structure in which an electrode assembly of a cathode/separator/anode structure is mounted in a battery case, and the battery case is sealed by thermal welding, wherein
 the secondary battery has at least one-way exhaust member, mounted at a sealed portion, formed at the outer circumference of an electrode assembly receiving part of the battery case, for allowing internal high-pressure gas to be exhausted out of a battery cell and preventing external gas from being introduced into the battery cell, 
 wherein the one-way exhaust member includes: 
 a first film attached to the sealed portion, 
 a porous film constructed in a structure in which the outer circumference of the porous film, excluding an upper end opening of the one-way exhaust member, is coupled to the first film, and the upper end of the porous film is lower than that of the first film, 
 a variable film constructed in a structure in which the outer circumference of the variable film, excluding the upper end opening of the one-way exhaust member, is coupled to the porous film, the lower end of the variable film is coupled to the porous film at a position where the lower end of the variable film is spaced apart from the lower end of the porous film by a predetermined width, and the upper end of the variable film is higher than that of the porous film, the variable film being made of a material more flexible than that of the porous film or having a thickness less than that of the porous film, and 
 a second film constructed in a structure in which the second film is attached to the sealed portion at the opposite side of the first film, and the outer circumference of the second film, excluding the upper end opening of the one-way exhaust member, is coupled to the lower end of the variable film, 
 wherein the first film, the porous film, the variable film, and the second film each have a longitudinal dimension, and wherein the longitudinal dimensions of the first film, the porous film, the variable film, and the second film all extend along a common direction. 
 
     
     
       17. The secondary battery according to  claim 16 , wherein the variable film is made of an elastic material, and the upper end of the variable film is bent toward the first film. 
     
     
       18. The secondary battery according to  claim 16 , wherein the upper end of the first film is in contact with the upper end of the second film during the normal operation of the battery. 
     
     
       19. The secondary battery according to  claim 16 , wherein the upper end opening of the one-way exhaust member is formed in the sealed portion such that the upper end opening of the one-way exhaust member communicates with the outside of the battery cell. 
     
     
       20. The secondary battery according to  claim 16 , wherein the porous film is a gas and liquid separation film.